It is known to provide a roving-bobbin frame formed by suspended roving bobbin carriages running on an overhead rail whereby the roving bobbins are positioned at a plurality of working positions of a yarn manufacturing spinning machine.
To avoid flaws in the drawing of the roving as a result of bobbin positioning inaccuracies the spatial arrangement of the roving bobbins must be maintained very exactly in the associated working positions.
In the suspended carriage the spacing of the roving spools can be maintained by the rigid structure of the bobbin holder in the bobbin carriage without great difficulty with the required tolerances. It is substantially more difficult to maintain the required spacing between the suspended carriages.
The suspended carriages are usually connected by coupling members to form a chain. These coupling members must be movable to allow the chain to pass readily along tight curves of the rail. The play in these coupling members and the additive tolerances for a large number of carriages lead frequently to the circumstance that an individual carriage or many suspended carriages may not be positioned with the required precision in regard to the set of drafting rolls associated with it.